Nip mechanisms typically, minimally comprise upper and lower nip rollers. These nip rollers extend parallel to each other and directly oppose each other. They are used to move substrates. In one typical mode of operation, the nip rollers are initially separated from each other, i.e., open, and a substrate is inserted between the nip rollers. The nip rollers are then brought together, i.e., closed, to engage the substrate between the two nip rollers. One or both of the nip rollers are then driven to transfer the substrate.
One application for nip mechanisms is in platesetters. In this example, the substrates that the nip mechanisms manipulate are termed plates. Plates are typically large sheets that have been coated with photosensitive or thermally-sensitive material layers. The plates are usually used in commercial printing operations. For large run applications, the substrates are fabricated from aluminum, although organic substrates, such as polyester or paper, are also available for smaller runs. Computer-to-plate printing systems are used to render digitally stored print content onto these printing plates. Typically, a plate management system supplies individual plates to the platesetter. A computer system is used to drive an imaging engine of the platesetter. The engine selectively exposes the surfaces of these plates. After exposure, the plates are supplied to post exposure processing equipment.
The nip mechanisms are used in the transfer systems that move the plate substrates between the management system and the platesetter. After exposure in the platesetter, another transfer system is used to move the substrate to the post processing equipment.
Typically, the nip mechanisms are driven by electric motors. The motors can include encoders to monitor how far the substrates have been transferred. Further, especially in platesetter systems, the nip mechanisms are usually opened and closed using pneumatic cylinders that are operated by solenoids.
Pneumatic operation in these platesetter systems is very common. Typically, there are many tubes for the routing of the pressurized air throughout the system in order to provide necessary actuation force to the various components of the machine.
However, as these platesetter systems, for example, become more complex, offering higher levels of functionality, the routing of the pneumatic lines can become problematic. As a result, it is sometimes desirable to replace pneumatic with, for example, electrical or mechanical actuation, especially if such replacement will decrease the overall complexity of the system. Moreover, each pneumatically driven function requires a separate solenoid to control the airflow to an actuation mechanism, such as an air cylinder. These devices add incrementally to the overall cost of goods in the manufacture of these systems.
The present invention is directed concerns a nip mechanism for a substrate transfer system. It allows the nip mechanism to be actuated, such as opened and/or closed, by a motor, such as the drive motor for the nip mechanism. As a result, when using the present invention, the need to operate the nip mechanism pneumatically can be avoided. Essentially, the drive motor now performs a dual role, i.e., both driving the nip rollers and also opening and closing the nip mechanism. Thus, for a slightly more complex mechanical system, a pneumatic operation can be avoided.
In general, according to one aspect, the invention features a nip mechanism for a substrate transfer system. It comprises a first nip roller and a second nip roller. A drive motor is used to drive the first nip roller and a second nip roller to feed a substrate between the first nip roller and the second nip roller, when the drive motor is driven in a first direction. According to the present invention, the drive motor actuates, such as opens, the nip mechanism by separating the first nip roller from the second nip roller when the drive motor is driven in a second direction.
According to the present embodiment, the inventive nip mechanism comprises a roller separation mechanism and a one-way clutch for engaging the roller separation mechanism when the drive motor is driven in the second direction. In the present implementation, this roller separation mechanism comprises a cam that pushes the first nip roller and the second nip roller away from each other. A cam limiter can be used to prevent over-rotation of this cam.
According to the preferred embodiment, a floating bearing block is used on either side of the second nip roller. This allows the second nip roller to be urged out of engagement from the first nip roller. In the preferred embodiment, the second nip roller is an upper nip roller and the first nip roller is a lower nip roller. As a result, the second nip roller is biased toward the first nip roller by gravity.
A downstream drive roller is preferably used for conveying the substrate downstream of the first nip roller and the second nip roller.
A nip mechanism for a substrate transfer system includes: a first nip roller; a second nip roller located substantially vertically above the first nip roller, and a drive motor for driving the first nip roller and the second nip roller to feed a substrate between the first nip roller and the second nip roller when the drive motor is driven in a first direction. The second nip roller creates and maintains a nip with the first nip roller due to a force of gravity without using a spring or other mechanical device while the drive motor is driven in the first direction. The drive motor engages a one-way clutch for engaging a roller separation mechanism to raise and separate the second nip roller from the first nip roller when the drive motor is driven in a second direction. The first and second nip rollers maintain substantial vertical alignment with one another when the drive motor is driven in either direction.
The above and other features of the invention including various novel details of construction and combinations of parts, and other advantages, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular method and device embodying the invention are shown by way of illustration and not as a limitation of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention.